RedEdge dark orthomosaics

[mikeyjump]

I've seen others reporting this, but no conclusive answers...

The RGB orthomosaics produced by my Micasense RedEdge surveys are generally very dark. I use reflectance panels for calibration with normalisation checked. I then produce the RGB by setting the raster calculator as below.

However the entire dynamic range of the RGB bands seems to be in the 0-0.1 range on the histogram, hence the dark images I guess. Is this normal or is something going wrong? It is recoverable if necessary, but seems odd.

[nprokofyev]

As I can see from your formulae, you are calculating reflectances, which range by definition is in 0..1.
And very "bright" material like paper has reflectance about 0.9. Gray micasense CRP panel's reflectance is about 0.5 and as you can see it is still appears quite bright for an eye.
In the picture, you are looking at red channel reflectance of a grass field, which absorbs red light extremely well due to chlorophyl content. 0.1 in red is totally ok for grass.

Secondly, you are working within linear range (without gamma correction). Normally, RGB images are applied gamma 2.2 while being saved to JPG. Without gamma correction the image looks darker for human eye.

Thus the answer is: it is fine. The image would have been "brighter" if you had applied gamma and/or adjusted resulting image levels.

(B3/32768)^0.4545

[mikeyjump]

Fantastic- that's very reassuring and has added to my knowledge - thank you!

(p.s. if you also replied to my Facebook post I'm further grateful)